Short-duration flares on T Tauri stars detected with Kiso Tomo-e Gozen at a 1 s cadence

Abstract

T Tauri stars (TTSs) exhibit more intense X-ray flares than main-sequence stars, driven by their strong magnetic activity. While X-ray surveys are primarily biased toward energetic events, optical observations of white-light flares are capable of detecting flares with bolometric energies of $E_{\mathrm{flare}} \lesssim 10^{36}$ erg. Here, we conducted $1\,\,{\rm s}$ cadence monitoring observations of over 200 TTSs toward the Taurus star-forming region using the wide-field Tomo-e Gozen camera on the 1.05 m Kiso Schmidt Telescope. The $1\,\,{\rm s}$ cadence enabled us to resolve the temporal structure of short-duration flares and precisely measure their energies. We detected seven flares with full width half maximum durations of 40–$10^3$ s and energies of $E_{\mathrm{flare}} \sim 10^{32}$–$10^{34}$ erg. These flares, combined with previous optical flare observations, reveal a trend consistent with the theoretical duration–energy scaling $\tau \propto E^{1/3}$. Furthermore, compared with flares on M-type main-sequence stars of similar energies, TTS flares exhibit comparable rise times but systematically longer decay times by a factor of ${\sim }2$. This difference might reflect sustained heating supplied by magnetic loops that are larger and more complex than those of main-sequence stars.